Circuits and systems operating simultaneously can share a reference signal that establishes a common time signal with which operations can be coordinated. One method with which this can be accomplished is with a clock signal that repeats at a given frequency and oscillates between a high and a low state.
Systems connected to the clock signal can synchronize their operations to the clock signal transitions. These synchronized operations can be used in signal processing, data transmission, and/or other types of time-sensitive data operations.
As a clock signal is shared across physical distances, the characteristics of the transmission medium as well as the distance itself can introduce skew into the clock signal as it is perceived by those elements of the system receiving the signal.
For example, clock signals can be implemented across the backplane of a communication system. A “master” clock can generate a master clock signal which is distributed to other elements of the system receiving the clock. These other elements may be timing cards or other types of integrated circuits. Because these signals may experience skew over the transmission distance, the system can provide other time synchronization elements to ensure that the elements receiving the clock signal are correctly synchronized.
One such time synchronization element is a Pulse Per Second (PPS) signal. In traditional systems a PPS signal may have a width of less than one second that repeats once per second. Because the PPS signal specifies a periodic designation of a second and not the actual time, it can be combined with other time source data that provides the full date and time to accurately establish the current time.
Traditionally a clock signal may be transmitted on a backplane of a communication system between cards for synchronization purposes.